Primary objective: To determine the safety and tolerance of intravenous infusions of anti-CD7 immunotoxin (DA7) when administered to therapy refractory T-lineage ALL and lymphoma patients in relapse and to define the MTD (maximum tolerated dose). Secondary objective: a) To obtain preliminary information on the effects of intravenous infusions of DA7 immunotoxin on the progression of T-lineage ALL and lymphoma following recurrence. b) to perform initial pharmacological studies to determine the volume of distribution, plasma clearance, in vivo chemical, immunological, and biological stability of intravenously administered DA7 immunotoxin, and if possible, the degree of in vivo binding and cytotoxicity of this immunotoxin to leukemic blasts in the circulation and bone marrow c) to assess whether and to what degree replapsed T-lineage ALL and lymphoma patients are capable of generation of antibodies directed against either the murine monoclonal antibody moiety Anti CD7 or deglycosylated ricin following repeated administration of the immunotoxin.